Erectile Dysfunction Flashcards
What is erectile dysfunction?
Persistent (at least 6 months) inability to achieve or maintain an erection of sufficient duration and firmness to complete satisfactory sexual intercourse
ED incidence increasing with ___
Age
around 50% of men 40yo and older experience ED
Describe the physiology of an erection
Flaccid state
- Arterial blood flow into penis = Venous blood flow out of penis
During erection
- Blood inflow > Blood flow out of penis
MOA of erection:
- Sexual arousal causes nerve to release chemicals that increase arterial flow into penis - Smooth muscle relaxes, corpora cavernosa fills up with blood, spongy muscle tissue relaxes and traps blood, makes penis firm
- Swelling causes compression of venules against tunica albuginea, which decreases venous outflow
What are the 2 systems that play a role in the physiology of an erection?
- Activated parasympathetic system
- Functional hormonal system
How does activation of parasympathetic system lead to an erection?
Sexual arousal causes acetylcholine release
- ACh increases Nitric Oxide (NO) which increases the activity of guanylate cyclase, and increases cyclic guanosine monophosphate (cGMP)
- ACh and Prostaglandins E increases adenyl cyclase, which increases cyclic adenosine monophosphate (cAMP)
cGMP and cAMP cause smooth muscle relaxation and vasodilation, hence increase blood flow
How does the functional hormonal system lead to an erection?
Testosterone encourages libido
Usual normal serum conc. of T: 300-1000ng/dL (10.4 - 38.2 nmol/L)
Describe the relationship between Testosterone levels and ED
Low testosterone does not mean ED
Normal testosterone can have ED
Hence, testosterone levels are only assessed in the perspective of presence of ED symptoms
Describe the physiology of Detumescence
(3 pathways)
- Deactivating of parasympathetic system
- cGMP deactivated by PDE-5 to 5-GMP (predominantly found in penis)
- stops the vasodilation and blood inflow - Activated sympathetic system
- induces smooth muscle contraction via a2 adrenergic receptors of arterioles resulting in a reduction of blood flow - Serotonin
- inhibitory effect on sexual arousal
- recall that a possible SE of SSRI is ED
What are the 4 etiology of ED?
- Organic ED (80%) - vascular, nervous, hormonal systems compromised, or medication induced
- Psychogenic ED - due to thoughts, feelings (e.g., malaise, loss of attraction, stress, performance anxiety, mental disorders, sedation)
- Mixed ED
- Others - social habits (smoking, alcohol, illicit drug use), obesity
Organic ED
Discuss the vascular causes of ED
Arteriosclerosis
Peripheral vascular disease
Hypertension
Diabetes (DM)
=> Associated with narrowed blood vessels, reduced inflow of blood to penis
Organic ED
Discuss the hormonal causes of ED
Hypogonadism - insufficient testosterone
Hyperprolactinemia - too much prolactin suppresses testosterone production
Organic ED
Discuss the nervous system causes of ED
Central: Spinal cord trauma or disorders, stroke, CNS tumors
Peripheral: Diabetes, Neuropathy, Urethral surgery
=> Associated with loss of sensation, nerve damage, nerve signals from brain or spinal cord do not reach penis
List examples of medication induced ED
A B C D 5 S
- Clonidine, Methyldopa, BB (except Nevibolol), Thiazide diuretics
- Anticholinergics (TCA, 1st gen antihistamines, phenothiazines)
- Dopamine antagonist (e.g., metoclopramide)
- Serotonin Selective Reuptake Inhibitors
- Finasteride, Dutasteride
- CNS depressants (e.g., Benzodiazepines, anticonvulsants)
- Clonidine, Methyldopa, BB (except Nevibolol), Thiazide diuretics
Explain MOA of ED, and alternatives
These are blood pressure (HTN) medications
MOA: Decrease penile blood flow
Alternatives: Nevibolol, ACEi, ARB, Loop diuretics
- Anticholinergics (TCA, 1st gen antihistamines, phenothiazines)
Explain MOA of ED, and alternatives
MOA: Anticholinergics decrease Acetylcholine activity, decrease parasympathetic activation
Alternatives: Bupropion, trazodone, 2nd gen antihistamines, 2nd gen atypical antipsychotics
- Dopamine antagonist (e.g., metoclopramide)
Explain MOA of ED, and alternatives
MOA: Dopamine causes sexual arousal and stimulation, hence antagonist reduces this
Alternatives: PPIs, erythromycin
- Serotonin Selective Reuptake Inhibitors
Explain MOA of ED, and alternatives
MOA: Increased serotonin in brain, serotonin has inhibitory effect on sexual arousal. Also decrease testosterone
Alternatives: Bupropion, Trazodone
- Finasteride, Dutasteride
Explain MOA of ED, and alternatives
MOA: decrease testosterone
Alternatives: (for BPH) Terazosin, Alfurosin
- CNS depressants (e.g., Benzodiazepines, anticonvulsants)
Explain MOA of ED, and alternatives
MOA: Suppress perception of psychic stimulus
Alternatives: Anticonvulsants (Valproic acid, Gabapentin) *less drowsy options
What are some complications of ED?
- Inability to achieve erection
- Loss of interest in sexual activities
- Depression
- Performance anxiety
- Embarrassment
- Angry
- Low self-esteem
- Disharmony in rsp
What are the parameters for evaluation of ED?
- Signs and symptoms
- SHIM score
- Workup to identify underlying causes of ED - medical, social, surgical history, lab results (BG, lipid, testosterone etc.)
- Evaluation for cardiovascular disease
Explain the Sexual Health Inventory for Men (SHIM) scoring system
Mild to no ED: 17-21 points
Moderate to severe: <11 points
*Lower points, severity increase